NETRA:Tool for Refractive Assessment

THE HUMBLE mobile phone is soon going to be your ophthalmologist. You will be able to self-test your eyesight just as you check your body temperature, blood pressure or blood glucose using digital devices. All you will need to do is run a simple application on your phone, look at the screen through a tiny attachment and press a few keys.

And within seconds, you will have the status of your eyesight on your phone's screen. This is an innovative piece of technology developed by a group of researchers led by India-born Ramesh Raskar at the media lab of the Massachusetts Institute of Technology (MIT).

It has yielded encouraging results and will soon be field-tested in India in collaboration with the Hyderabad-based L. V. Prasad Eye Institute.

The device has been named NETRA or Near-Eye Tool for Refractive Assessment. The device has the potential to make routine eye-testing simpler, cheaper and accessible to millions of people. It takes advantage of the huge improvements in the resolution of digital displays and their widespread proliferation on mobile phones, which have become ubiquitous in developing countries.

NETRA currently works with phones having high-resolution displays. But researchers are expanding the range of phones that it can work on and are also developing pattern designs that can work with low-resolution phones.

"You can think of it as a thermometer for visual performance. Just as a thermometer measures corporal temperature and does not prescribe medicine, NETRA measures the refractive error and does not necessarily prescribe glasses," says Raskar, who heads the Camera Culture group at the media lab. "It allows a user to self- assess the performance of his or her eyes over time. The goal is to empower people, not replace optometrists."

Apart from the software to run on the phone, all that's needed is a snap-on plastic device, which, researchers say, can be produced for about $2 (about Rs 93). But it would cost much lesser if produced in large quantities. The plastic device can be clipped on to the front of a cell phone's screen.

The micro-lens array in front of the LCD essentially creates a 4D display. The user looks into a small lens and presses the phone's navigation keys until sets of parallel green and red lines overlap. This is repeated eight times, with the lines at different angles, for each eye.

The whole process takes less than two minutes, at which point the software loaded on to the phone provides the prescription data. The prototype developed by Raskar's team has an array of tiny lenses and a grid of pinholes that, combined with the software on the phone, forces the user to focus at different depths.